Not applicable.
Not applicable.
The present invention generally relates to telecommunication networks, and more particularly to a system and method for providing carriers the ability to offer switched virtual circuit services to customers for frame relay communications.
Frame relay is a high performance, cost-effective means of connecting an organization""s multiple LANs and systems network architecture (SNA) services through the use of various techniques. Like the old X.25 packet-switching services, frame relay uses the transmission links only when they are needed. Frame relay was created using the benefits of the switched network and the packet arrangements of previous networks.
Asynchronous Transfer Mode (ATM) is similar in concept to frame relay. Both take advantage of the reliability and fidelity of modem digital facilities to provide faster packet switching than X.25. ATM, at its higher data rate, is even more streamlined in its functionality than frame relay. ATM is a network technology capable of transmitting data, voice, video, and frame relay traffic in real time. Data, including frame relay data is broker into packets containing 53 bytes each, which are switched between two nodes in the system at rates ranging from 1.5 Mbps to 622 Mbps. ATM is defined in the broadband ISDN protocol at the levels corresponding to levels 1 and 2 of the ISO/OSI model, which are the physical layer and data-link layer. In computer networks, the physical layer is responsible for handling both the mechanical and electrical details of the physical transmission of a bit stream. At the physical layer, the communicating systems must agree on the electrical representation of a binary 0 and 1, so that when data are sent as a stream of electrical signals, the receiver is able to interpret the data properly as binary data. This layer is implemented in the hardware of the networking device. The data-link layer is responsible for handling the frames, or fixed-length parts of packets, including any error detection and recovery that occurs in the physical layer. Although this technology has traditionally been used in local area networks involving workstations and personal computers, it has now been adopted by telephone companies.
As is known, time-division multiplexed (TDM) circuit switching creates a full-time connection or a dedicated circuit for the duration of the connection, between any two attached devices. TDM divides the bandwidth into fixed time slots, that allow multi-channel communication. Specifically, multiple devices may communicate across a single physical line, by being assigned one of the TDM time slots. Unfortunately, when an attached device is not sending data the time slots remain empty, thereby wasting the use of the bandwidth. Hence, a higher speed device on the network can be slowed down or bottled up waiting to transmit data, but the capacity that sits idle cannot be allocated to this higher device for the duration of the transmission. Thus TDM is not well suited for burst data transmissions which are common.
As is further known, X.25 packet-switching was created to solve the limitations of the fixed bandwidth allocation of TDM circuit switching. X.25 packet switching allowed the bandwidth to be allocated on the fly. Instead of putting the data into a fixed time slot, the user data is broken down into smaller pieces called packets, each containing both the source and the destination addressing information, as well as other control functional information. When a-user sends data in a burst, multiple packets will be generated and routed across the network based on the address information contained in the packets. The network creates a virtual circuit between each source and destination to keep track of the packets on each connection. Multiple virtual circuits can be active on the same line. This form of multiplexing is called statistical time-division multiplexing (STDM). STDM uses the analyses of the past users to allocate more interleaved packet slots to the heavier users and less interleaved packet slots to the lighter users. Although guaranteed delivery and integrity was a prerequisite for the development of the X.25 networks, the major drawback to this scheme is the penalty paid in speed of delivery. Taking the features of the switched network and the packet arrangements, the network arrived at a frame relay service.
The increased need for speed across the network platforms within the end user and the carrier networks was one reason why frame relay was developed. The need for higher speeds has been driven in part by the move away from the original textbased services to the current graphics-oriented services and the bursty time-sensitive data needs of the user through new applications. The proliferation of LANs and client/server architectures that are being deployed have shifted the paradigm of computing platforms. To accommodate this new paradigm of availability, speed and reliability of communications between systems and services, reduced overhead associated with the network by eliminating some of the processing, mainly in the error detection and correction schemes were introduced. Frame relay was designed to take advantage of the network""s ability to transport data on a low-error, high-performance digital network, and serve the needs of the intelligent synchronous applications of the newer and more sophisticated user applications. Analog transmission systems were extremely noisy and produced a significant amount of network errors and data corruption. Digital networks are much more dependable with respect to integrity of data transmissions.
Frame relay makes the design of the network much simpler than using a mesh of private leased lines. In frame relay, instead of having a costly private leased line between each site requiring communications requiring a large number of leased lines, frame relay access from each site is provided into a network cloud, requiring only a single connection point. Data transported across the network is interleaved on a frame-by-frame basis. Multiple sessions can be running on the same link concurrently. Communications from a single site to any of the other sites can be easily accommodated using the pre-defined network connections of virtual circuits. In frame relay, these connections use permanent logical links (PLL), more commonly referred to as permanent virtual circuits (PVC). In contrast, switched virtual circuits (SVC) are logical connections which are not permanent, but only established when data is to be transmitted. Each of the PVCs and SVCs connects two sites just as a private line would, but in this case the bandwidth is shared among multiple users, rather than being dedicated to one site for access to a single site. Using this multiple-site connectivity on a single link reduces the costs associated with customer premises equipment, such as CPU ports, router ports, or other connectivity arrangements.
When designing a frame relay service, the speed of access is important to manage, both prior to and after installation. First, customers ask a service provider to provision a PVC, if they plan to communicate through frame relay often. The PVC is used to communicate between two sites exclusively. The customer must select and be aware of the need for a specified delivery rate. There are various ways of assigning the speed, from both an access and from a pricing perspective. The flat rate service offers the speed of service at a fixed rate of speed. The pay-as-you-go service is usage-based and might include no flat rate service. The combined service is a mix of both offerings. The customer selects a committed information rate (CIR) at a certain speed. The committed information rate is a guaranteed rate of throughput when using frame relay. The CIR is assigned to each of the PVCs selected by the user. Each PVC should be assigned a CIR that is consistent with the average expected volume of traffic to the destination port. Because frame relay is a duplex service (data can be transmitted simultaneously in each direction), a different CIR can be assigned in each direction. This allows added flexibility to the customer""s needs for transport. However, because LAN traffic is generally bursty, the CIR can be burst over and above the fixed rate for a period of less than two seconds at a time in some carrier networks. The variable PVC arrangement with differing CIRs is a flexible arrangement. However, care must be taken when customers use this arrangement because there is a fee associated the port on the switching node within the network that can be substantial.
As aforementioned, SVCs are not permanent. SVCs are used to communicate to a remote site in which the customer has not set up a PVC. SVCs can also be used along with PVCs for additional bandwidth. SVCs get signaled similar to X.25 packet switching and involves call setup and call takedown. An address is given to communications switches, such as frame relay switches, inside the network and the frame relay network will communicate and set up the path based on the address. When a PVC is provisioned the path from end-to-end is set up. In a SVC, the path can vary depending on changes that are made internal to the network. SVCs can therefore eliminate the need for a customer to set up a dedicated PVC to a site which is not communicated with often. Also, since SVCs can be used to communicate with various sites, it can eliminate the need for the customer paying for more bandwidth initially than is needed. Although SVCs are currently not very popular, systems are known which allow PVCs and SVCs to exist simultaneously on a single switch.
Over time, increasing CIR, PVC and port charges often offset the savings initially provided by migrating to frame relay. Frame relay access products are known to combat this erosion of savings through selective data compression, port aggregation and PVC multiplexing. In a system that does not rely on a router for compression or data prioritization, the router is less burdened, which can improve network performance. This can also displace the need to upgrade the router. A data link control identifier (DLCI) is a portion of a frame that marks the PVC addressing scheme thereby allowing customers to reduce the number of physical ports and share a single PVC for multiple data streams, including inband simple network management protocol (SNMP) management. All routers that provide frame relay interfaces can be configured to provide PVCs between the router and the frame relay access unit. However, some service providers provide SVC services which are advantageous in alleviating the problems with meshed and partially meshed networks, as well as disaster recovery when the PVC link between two sites fail, but implementation at the customer site requires additional hardware or upgrades to existing hardware and software. Routers are not generally adapted to handle SVCs and routers may come from many different vendors having many different architectures. Those routers that are adapted to handle SVCs are very costly. Another solution to the problem of CIR, congestion and disaster recovery currently is to have multiple PVCs. This is also costly to the customer and is often inefficient, when not fully or at least substantially utilized.
There is therefore a need in the industry for a method and apparatus for addressing these and other related problems.
Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the advantages and novel features, the present invention is generally directed to a method for mapping VCs that are seldom used from a router into SVCs of a service provider frame relay network, based on various criteria from system evaluation. In accordance with one aspect of the invention, the system establishes an SVC to aid or replace a PVC for communication upon request by the a site or upon adverse network conditions. The system provides for the mapping of DLCI(s) on the port side (router) to an address on the network side which corresponds to the destination unit. The destination unit is a router supporting SVCs or a frame relay access device which supports VC/SVC conversion.
According to an aspect of the invention, a VC/SVC conversion will occur upon detection of data on a VC from the router configured to be mapped to an SVC.
According to another aspect of the invention, a VC/SVC conversion will also occur upon receipt of a SVC call from the network that is configured to be mapped to a VC from the router.
According to yet another aspect of the invention, a VC/SVC conversion will occur during a specified time of day. The VC/SVC converter contains a timer which will set up and take down the SVC during certain times of the day when a VC is not available or is heavily used. The VC/SVC conversion may also occur when a VC fails or is otherwise unexplainably interrupted for a period of time. In this case, an SVC is activated as an alternate link for backup (disaster recovery).
The present invention has many advantages, a few of which are delineated hereinafter, as examples.
An advantage of the VC/SVC conversion system and method is that they allow a Carrier providing SVC service to avoid having to upgrade/replace the customer""s existing premises equipment to support SVC.
Another advantage of the VC/SVC conversion system and method is that they allow the customer more bandwidth for communication on demand.
Another advantage of the VC/SVC conversion system and method is that they allow disaster recovery for VC links which fail to communicate.
Another advantage of the VC/SVC conversion system and method is that they provide load balancing of communication on VCs experiencing congestion or exceeding the CIR.
Another advantage of the VC/SVC conversion system and method is that they provide an alternate link of communication during a specific time of the day, when the user may need more bandwidth or the PVC is unavailable.
Another advantage of the VC/SVC conversion system and method is that they enable communication to remote sites which may not.be reachable by a VC.